Warren Buffett famously quipped that you can’t tell who is swimming naked until the tide goes out.

Well, the waters supporting San Diego County’s pension fund have been receding lately, siphoned by losses in bond, commodity and foreign markets.

Now one of the officials charged with protecting the investments of taxpayers and retirees is taking a hard look at the fund’s exotic, supposedly low-risk investment strategy.

Last month County Supervisor Dianne Jacob, who serves on the pension fund’s board, told investment officials that she was concerned about how the fund’s Treasury bond portfolio was being managed in the wake of heavy losses in May and June. And she asked for a thorough review of the fund’s use of leverage.

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Ordinarily, Jacob’s alarm over short-term losses would send me into a tizzy. Overreaction to market fluctuations is precisely why individual investors — and most fund managers — tend to sell at the bottom and buy near a market top.

Yet in this case I’m delighted. Sticking to your guns is admirable only if you have the right investment strategy and a skilled practitioner.

But San Diego County’s pension board has chosen a strategy that is expensive and far riskier than advertised.

It’s possible that the architect of this strategy, consultant Lee Partridge, is in fact a skilled practitioner. Or he may have been lucky.

Since the board hired him in October 2009, the fund’s investments have grown in value at an average annual rate of 9.3 percent.

Although that lags the performance of the S&P 500 stock index since then, it’s better than the average traditional pension fund with a portfolio of 60 percent in blue-chip U.S. stocks and 40 percent in top-rated bonds. It also beats some benchmarks that seek to simulate a broadly diversified portfolio.

However, it’s also possible that the county’s luck has turned, highlighting the inherent vulnerabilities of Partridge’s particular approach to diversification.

Partridge reported this month that he substantially underperformed his peers in the fiscal year that ended June 30, as bad bets on bonds, commodities and foreign securities produced losses in recent months that cut into previous gains from investments in U.S. companies and real estate.

Overall, San Diego County’s portfolio grew in value by 7.8 percent during the year, compared to an average of nearly 13 percent in a peer group. The fund for San Diego city workers grew by 13.4 percent. Sonoma County’s fund gained 15.3 percent.

Yet the news for local taxpayers gets worse.

The county fund pays about $7.2 million a year to Partridge and his firm, Salient Partners. Tens of millions more go to fund managers picked by Partridge.

Meanwhile, the investment strategist for San Diego’s city pension system makes under $200,000 a year. Although additional city employees do some of the work that is done for the county by Salient, I’d be surprised if the annual staff cost is more than a tenth of $7.2 million.

The members of the county’s pension board are no dummies. So why are they paying so much for fund management? I fear the answer boils down to hubris, along with a strange susceptibility to investing fads.